35Rem ! I have used the 225438 bullet cast from ww and 3 gr of unique ,and small rifle primers at 100yds for years and it shoots better then my rimfires ! First clean the jacket fouling out of your barrel, all of it , use JB bore past , then check for the case length if to long , and trim if need to ! I use this bullet both with and without GC and Alox an Bee lube ! You can also try 3.5 grains with your K hornet ! JAGG